Passive Radar

Gizmodo reports: "Fascinating article in BusinessWeek about Celldar, a 'passive' radar system that sort of piggybacks on the whole cellphone network to track almost any moving object anywhere. It works by using complex signal-processing software to interpret how signals from cellular base stations bounce off of and interact with boats, planes, cars, and maybe even people, and costs considerably less than traditional radar systems. "

This is news to me. Just making a note of it. More from Business Week:
Celldar's implications are exciting -- but also troubling to some. Even though the technology can't be used to identify cell-phone users, since it "sees" only radio waves echoing off hard surfaces, it and similar approaches are evolving quickly. In addition to Celldar, which is sopping up $1.5 million a year for development, a dozen other passive-radar projects are under way in the U.S., Europe, and Asia. As the technology bears fruit, it should give the world's police and homeland security agencies new tools for monitoring shipments of illegal weapons and drug smuggling operations. Highway officials could gain a detailed window on traffic flows, helping them to minimize congestion. But because passive-radar systems could be cheap enough for hobbyists to buy -- or cobble together themselves -- the technology could also become the next fad among people who own police-radio scanners or who enjoy snooping on their neighbors' comings and goings. late October, radar researchers from around the world will gather in Seattle to discuss recent advances, including passive systems that use FM radio or TV broadcasts instead of cell-phone signals. The invitation-only meeting will be hosted by John D. Sahr, a University of Washington electrical engineer. Since 1997 he has operated a passive-radar system unshrouded by military secrecy. It harnesses an FM station's signals to study particles in the ionosphere -- the top layer of the atmosphere, over 300 miles up. Sahr decided to go with passive radar, he says, "because it's incredibly cheap" -- $20,000 vs. $25 million for a comparable active system. "You could probably do an amateur system for under $5,000," Sahr adds. A system for small airports might cost as little as $15,000. That's important because of the 5,280 public airports in the U.S., only about 300 currently have radar.

STRONG SIGNALS. Lockheed-Martin Corp. (LMT ) is perhaps the best-known passive-radar champion, but others include Avtec Systems, Dynetics, and ONERA, the French counterpart of NASA. Lockheed-Martin's system is dubbed Silent Sentry. Last fall, in a demo for the U.S. Air Force, a third-generation Silent Sentry radar tracked all the air traffic over Washington, D.C., by picking up FM and TV echoes. Because FM and TV transmissions are more powerful than their cell-phone cousins, Silent Sentry can detect planes as far away as 135 miles, roughly 10 times the reach of an individual cell-phone tower.

However, because cell-phone towers are scattered far and wide in many countries, an airborn Celldar system "could covertly monitor a whole country" by flying along its borders, says Lloyd...

Despite Celldar's military potential, Lloyd predicts the first applications will come in the civilian sector. He says transportation officials are eager to use Celldar to monitor road traffic because it would avoid the expense of installing either sensors in roads or TV cameras overhead. And police cars equipped with Celldar could follow a car driven by a suspected crook or terrorist from a safe distance, without danger of being seen.

TRACKING MADE CHEAP. Celldar might also provide an alternative to the global positioning satellite (GPS) systems now being explored by insurance companies and governments for monitoring vehicles. Their goal is to set premiums individually, based on how much and how fast each car or truck is driven -- or to levy a road-use toll determined by the distance a vehicle travels, over which types of roads, and at what times of day. In Ireland, AXA Insurance is testing a GPS gadget called Traksure. It continuously checks a car's speed and location, then compares that data with the local speed limit, obtained from digital maps. But Celldar might do the job more cheaply.

And it might support schemes by Oregon and other states regarding "pay-for-use" road taxes. Many transportation experts assert that taxing actual driving distances would be a more equitable way of funding highway upkeep than today's tax on gasoline and diesel fuels. That's why the European Commission wants every vehicle in Europe to be fitted by 2010 with a black-box device that can be tracked by satellite. Germany is now testing such a system on trucks, and Britain plans to require it on trucks by 2006...